Magnetic switching device



Dec. l0, 1957 R. L. WHITELY 2,816,278

MAGNETIC swITcHING DEVICE Filed oct. 1, 1954 ff L1* 655-25 -v 662W vX//v Z0 4Z a Z 4Z ,V007

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Wife/y United States Patent MAGNETIC SWITCHING DEVICE Richard LawtonWhitely, Haddoniield, N. J., assignor to Radio Corporation of America, acorporation of Dela- Ware Application October 1, 1954, Serial No.459,662

8 Claims. (Cl. 340-174) This invention relates to digital informationhandling systems, and particularly to magnetic devices for performinglogical and switching functions in such digital systems.

A number of disadvantages have been encountered in `the development ofvacuum tube circuits for digital cornputers. These disadvantages includetube failures, large power-supply requirements and large size. Toeliminate such disadvantages in certain applications, magnetic systemsnave been developed that employ magnetic cores made otmaterial having asubstantially rectangular hysteresis characteristic. These magneticsystems have me advantages of small size, relatively small power-supply,and relatively long life.

Among such magnetic systems that have been developed heretofore arethose employing magnetic ampliiiers. In such asystem, for example, amagnetic amplifier unit is used to perform various storage, logical, andswitching functions including the functions of a storage register, aflip-flop, and an and circuits.

Accordingly, it is among the objects of this invention to provide:

A new and improved magnetic device for performing logical and switchingfunctions;

An improved and simple magnetic device for performing logical andswitching functions that is reliable in operation;

An improved magneticdevice for performing logical operations that iseconomical in construction;

An improved apparatus for performing storage and switching operations.

In accordance with this invention, a magnetic device includes asaturable magnetic core and circuit means for driving the corealternately from an initial state of saturation to the opposite stateand back to the initial state. This circuit means includes a windinglinked to the core, and means for applying pulses of alternatelyopposite polarities to the winding. Means are employed for applyinginput pulses to the circuit means to inhibit those pulses that tend todrive the core from the initial state. A load impedance is conneced inseries with the winding and both pulse applying means in the same seriescircuit. An output pulse is produced across the load impedance only uponthe occurrence of an input pulse. A stepping register may .be providedby connecting in cascade a plurality of these devices. A magnetic deviceaccording to this invention may have an output circuit that includesanother winding linked to the core, a unilateral impedance and a loadimpedance. This output circuit produces an output pulse only in theabsence of an input pulse and when there is a change of state of thecore.

The foregoing and other objects, the advantages and novel features ofthis invention, as well as the invention itself both as to itsorganization and mode of operation, may be best understood from thefollowing description when read in connection with the accompanyingdrawing, in which like reference numerals refer to like parts, and

in which:

Figure 1 is a schematic circuit diagram of a magnetic stepping registerembodying this invention;

Figure 2 is an idealized graph of a hysteresis curve of a magnetic coreused in the device of Figure 1;

Figure 3 is an idealized graph of waveforms occurring in portions of thecircuit of Figure 1 and Figure 4; and

Figure 4 is a schematic circuit diagram of another embodiment of thisinvention.

Referring to Figure 1, a plurality of magnetic devices 10, 12, 14, 16are connected in cascade as a stepping register. The devices 10, 12, 14,16 are the same, except where noted below. Therefore, only the firstdevice, 10 is described in detail. A saturable magnetic core 18 isemployed that preferably has a substantially rectangular hysteresiscurve of the type shown in Figure 2. Desirable characteristics of thecore material are a high saturation ux density Bm, a high value ofresidual liux density Br and a low coercive force Hc. Oppositedirections of flux in the core 18 are represented by P and N.

A winding 20 is linked to the core 18 and is connected at one end to oneof a pair of input terminals 42, the other of which is connected to areference potential shown as ground. The other end of winding 20 isconnected to a load circuit 24. The load circuit 24 includes a resistor26, a direct voltage source shown as a battery 28 and a diode 30, allconnected in series in the same loop and with the diode 30 poled to passcurrent from the positive battery terminal to the resistor 26. Thejunction of the diode 30 and resistor 26 is connected to the coil 20.The junction of the diode 30 and battery 28 is connected to one terminal34 of a pair of alternating current (A.C.) terminals 32, 34. The A.C.terminals 32 of the first and third devices 10, 14 are connected toground, as are the A.-C. terminals 34 of the second and fourth devices12, 16. The A.C. terminals 34 of the first and third devices 10, 14 areconnected to one end of the secondary 36 of a transformer, as areterminals 32 of the second and fourth devices 12, 16. The other end ofthe transformer secondary 36 is grounded. An A.C. source 40 is connectedto the primary 38 of the transformer. The pulse source 40 may include asine-wave oscillator (not shown). Thus, the same A.C. power supply isused for all the devices 10, 12, 14, 16. The input terminals 42, A.C.terminals 32, 34, load 24 and winding 20 of each device 10, 12, 14, 16are connected in the same series circuit.

The input to the rst device 10 may Ibe the output of a precedingmagnetic device (not shown). Under such circumstances, the load circuitof that preceding device is connected between input terminals 42. Theload circuit 24 of device 10 is connected between the input terminals 42of the succeeding magnetic device 12. In the same manner, the outputload 44 of the second device 12 is the input load of the third device14, and so on. The voltage across the output load 46 of the last device16, at the terminals 48, is the output voltage. The A.C. voltage atterminals 32, 34 of the lirst and third devices 10, 14 and of alternatesucceeding devices (not shown) is a half cycle out of phase with respectto the voltage at terminals 32, 34 of the second and fourth devices 12,16 and alternate succeeding devices (not shown).

Waveforms occurring in portions of the circuit of Figure l are shown inFigure 3. The core 13 of the rst device 10 is assumed to be initially instate N. The A.C. voltage applied to the terminals 32, 34 may be a sineWave E. The first half cycle of the sine wave is hereinafter called apositive pulse, and the second half cycle a negative pulse. The inputpulses at terminals 4.?. of the first device 10 are positive-going withrespect to ground and are substantially coincident with the first halfcycle of E. Shown in Figure l are the relative polarities of thevoltages at A.C. terminals 32, 34 existing during time interl val 1. Atthat time, it is assumed that there is no input pulse. A positive-goingpulse is applied to the A.-C. terminal 34 of the first device 10 whichis passed by diode 3th of the output load circuit 24 through winding 2@to ldrive coreslfrom state-N to state P. During time interval 2, thepulse applied to terminal 34 of the irst devicefll is negative-going,andthe core 13 is driven from state P back to state -N. Substantiallythe 'full voltage `E is dropped across the impedance of the winding-2ll.in reversing the state of the core, and there is a negligible yoltagedrop due to E across the output load The current in the outputloadcircuit 245- due to the battery 2S and the resistor 26 is of the orderoftwice the magnetizing current lthrough the winding 2t? produced by E.During the second half cycle of E, the magnetizing currents throughwindings Zii of the rst and second dcvices-lltl, l2 lflow in the samedirection through load 2id. The current flow through the diode 3l) ofload 24 is substantially blockedl bythe sum of these magnetir/ingcurrents, but the net current through resistor 25 remains substantiallyunchanged. Thus, there is substantially no voltage change-acrossresistor 26. Accordingly, in the absence ot an input pulse, the first orsetting half-cycle of E drives the core 18 of the lirst device lt) to P,and the second or resetting half-cycle of E returns the core to Nwithout producing an output pulse.

During time interval 3, it is assumed that there is an input pulse thatopposes the positive-going setting pulse at A.C. terminal 34. As aresult, the winding Ztl is not energized and the core lil remains instate N. During time interval 4l,V the negative-going resetting pulse atterminal is presented with a negligible impedance in the winding Ztl dueto the core 18 already being in state-N.

Substantially the full voltage E is applied across -the load impedance24 and there is a positive-going output pulse approximately equal inamplitude to E.

rhe second device l2 operates in the same manner onelialf cycle behindthe rst device liti, that is, the core lg of the second device l?,is-being set to state P at the same time the core 18 of the irst deviceis being reset to state N. It has been shown that in the absence of aninput pulse, there is no output pulse across load 24 a halt cycle later.When the rst device liti is being reset, and the second device l2 isbeing set, the positive pulse E at terminal Srl-of the second device l2is not inhibited by anyoutput from the iirst device lil. Thus, afteranother half-cycle delay, the seconddevice 12 produces an Youtputfin theform of an absence of a pulse. lNhen there is an input pulse at theterminal d2, there is an output pulse produced across the load 24. ofthe rst device l0 that is delayed a half cycle after the input pulse. Atthis time, the second device l2 is being set and its positive-goingpulse E is inhibited. yAt the next half cycle,

therefore, there is an output pulse produced across the lcfad Theremaining devices lll, i6 of the stepping register operate in the samemanner to step along the input signals in the formof a pulse or theabsence of a pulse with a half-cycle delay from one device to the next.

VEach of the magnetic devices l0, l2, ld and 16 ot Figure l may bemodiiied in the manner shown in Figure 4 for the second device 12. Thesame reference numerals are employed imparts-previously described. Asecc-nd winding Sti is linked to the core liti. Connected in series withthe winding 'Sti Vis a diodeSZ and an output load da. The output load 54may be similar to the load shown in Figure l. The junction of the diodeEl@ and resistor 26 of the load 54 is connected to the cathode ot thediode :32. The junction of the battery 23 and diode 3i: of the load 54is connected to the winding 50.

The relative senses of linkages of thewindings Ztl and and the polarityof the diode 52 are such that current flows in the forward directioninthe diode 52 only when the core i8 is driven to state P only in theabsence of an -inputpulse Therefore, a pulse is passed by diode 52 inthexforwardcdirection, whenpthecore 18 is returned to state N, whichoccurs only when an input pulse was absent during the previous halfcycle. An output pulse is produced across the load 54 only in theabsence of an input pulse. When there is an input pulse, core l does notchange its state so that there is no output pulse. Thus, by the additionof circuit 56, the logical operation of negation (that is, X') may alsobe provided. Where the negation output X is desired without a half-cycledelay, the relative senses of linkage of coils 2d and l50 may bereversed. ln that case, the diode 52 passes a pulse when the core i3 isdriven to state P.

it is seen from the above description of this invention that an improvedmagnetic device is provided for switching and logical operations. Thecircuit is simple, reliable in operation and economical in construction.

What is claimed is:

l. A magnetic device comprising a magnetic element, a winding linkingsaid magnetic element, means for applying pulses of alternately oppositepolarities to said winding in a sense 'tending to drive said elementalternately from an initial state and back to said initial state, meansfor applying input pulses to said winding to oppose those `of saidopposite polarity pulses tending to drive said elevfrom an initial stateand back to said initial state, means for applying input pulses to saidwinding to oppose those of said opposite polarity pulses tending todrive said element from said initial state, and a load impedance, saidwinding, both of said pulse applying means, and said load impedancebeing connected in series with each other in the same series circuit,wherein said load impedance includes a resistor, a direct voltage sourceand a unilateral impedance connected in a series loopsaid unilateralimpedance and said resistor being connected to said winding to provideparallel current paths for said opposite polarity pulses.

3. A magnetic device comprising a magnetic element, a winding linkingsaid magnetic element, means for applying pulses of alternately oppositepolarities to said Winding in a sense tending to drive said elementalternately fro-rn an initial state and back to said initial` state,means -for applying input pulses to said winding to oppose those of saidopposite polarity pulses tending to drive said element' from saidinitial state, and a load impedance, said winding, both of said pulseapplyingmeans, and said load Vimpedance being connected in series witheach other in the `same series circuit, and further comprising means forproducing output pulses only in the absence of said input pulsesincluding anotherwinding linked to said magnetic element.

4. Apparatus comprising a plurality of magnetic de- Y Vices, each ofsaid magnetic devices including a separate magnetic element, a windinglinking said magnetic element, means for applying pulses to said windingin a sense tending todrive said element alternately from an initialstate andback to said initial stateand a load impedance `from saidlinitial state, and means connecting said viirst device load impedance inseries with said. winding and said loadimpedanceof asecond one. of saiddevices in the same series circuit. i A i 4 5.,,Apparatusrcomprising a.plurality ofmagneticdeyices, eachncfsaidrmagnaetic devices .including aseparate magnetic element, a winding linked to said magnetic element, apair of iirst terminals connected to -said Winding, a pair of secondterminals connected to said winding for applying input pulses thereto,and an output load impedance connected in series with said winding andsaid rst terminals, said apparatus further comprising means connectingsaid load impedance of each of said devices between said secondterminals of a diierent succeeding one of said devices, means forapplying a reference potential to one of said rst terminals of each ofsaid devices, and a common alternating power supply connected to theother of said first terminals of each of said devices.

6. Apparatus as recited in claim 5 wherein said rst and secondterminals, said winding and said load impedance of each of said devicesare connected in series with each other in the same series circuit.

7. A magnetic device comprising a magnetic element, circuit means foralternately applying magnetomotive forces of opposite polarities to saidelement to drive said element alternately from an initial magnetic stateand back to said initial state, said circuit means including a windinglinked to said element, and means for applying pulses of alternatelyopposite polarities to said winding, impedance means for applying inputpulses to said circuit means to inhibit those of said opposite pulsestending to drive said element from said initial state, and outputimpedance means including a diode for producing output pulses upon theoccurrence of said input pulses, said winding, both of said pulseapplying means and said output impedance means being connected in serieswith each other in the same series circuit.

8. A magnetic device comprising a magnetic element, circuit means foralternately applying magnetomotive forces of opposite polarities to saidelement to drive said element alternately from an initial magnetic stateand back to said initial state, said circuit means including a windinglinked to said element, and means for applying pulses of alternatelyopposite polarities to said winding, impedance means for applying inputpulses to said circuit means to inhibit those of Asaid opposite pulsestending to drive said element from said initial state, and outputimpedance means for producing output pulses upon the occurrence of saidinput pulses, said winding, both of said pulse applying means and saidoutput impedance means being connected in series with each other in thesame series circuit, wherein said input pulse impedance means and saidoutput impedance means each includes separately a resistor, a directvoltage source and a unilateral impedance connected in a series loop,said unilateral impedance and said resistor being connected to saidwinding to provide parallel current paths for said opposite polaritypulses.

OTHER REFERENCES Publication I, AIEE Transactions, part I,Communications and Electronics, pages 442-446, January 1953.

